You want to keep your per-mailing email bounce rate under:

Maintaining a per-mailing email bounce rate of 20% or lower is crucial for the health of your email marketing campaigns. A bounce rate refers to the percentage of emails that could not be delivered to the recipient's inbox. High bounce rates can damage your sender reputation, which is a critical factor in ensuring your emails reach your audience successfully. If your bounce rate exceeds this threshold, it signals to email service providers that you might be sending to invalid or outdated email addresses, leading to deliverability issues in the future.

In addition, an email bounce rate of 20% or lower is considered a best practice within the industry. Staying under this threshold helps in maintaining a good sender reputation, improves engagement rates, and enhances overall campaign performance. This standard allows marketers to proactively manage their email lists, ensuring that they regularly clean and update their subscriber databases to prevent high bounce rates. By keeping the bounce rate within these parameters, businesses can foster better relationships with their customers and ensure higher engagement with their email campaigns.